1. Field of the Invention
This invention relates to an injector mounting structure in an engine in which fuel injection is performed by injectors via a common rail (pressure accumulator).
2. Description of the Related Art
In a diesel engine, for example, fuel from a high pressure fuel pump is sent to a common rail (pressure accumulator), and fuel injection is performed by injectors via the common rail. With the diesel engine, therefore, the high pressure fuel pump and the common rail are connected by fuel supply pipes, and the common rail and a plurality of the injectors are connected by fuel pipes. Return pipes are provided between the common rail/the injectors and the high pressure fuel pump.
As a structure for mounting the injectors, a proposal has been made for a structure in which the injectors are mounted at predetermined positions of a cylinder head through a cylinder head cover, and fixed from outside the cylinder head cover via clamp members (see, for example, JP-A-2002-310040). A proposal has also been made for a structure in which fuel pipes for supplying fuel to the injectors are connected to the injectors outside the cylinder head cover (see, for example, JP-UM-B-61-549).
In the diesel engine, the cylinder head cover is detached, and valve clearance adjustment, etc. are carried out periodically for maintaining gas emission performance, noise suppression, and so on. For this purpose, the injector mounting structure disclosed in JP-A-2002-310040 has required that the clamps for the injectors fixed to the cylinder head cover be removed, the injectors detached, and the cylinder head cover detached. With the injector mounting structure disclosed in JP-UM-B-61-549, it has been necessary to remove the fuel pipes outside the cylinder head cover, disconnect the injectors and the common rail, then detach the injectors, and detach the cylinder head cover.
With the injector mounting structures proposed thus far, many man-hours and work hours have been necessary in detaching the cylinder head cover and making valve clearance adjustment, etc. periodically. Moreover, the high-pressure fuel pipe is usually connected by a flare nut (by a flare mechanism). Thus, the number of its attachments and detachments is limited, and the repetition of attachment and detachment of the fuel pipe lowers the reliability of the flare mechanism. Hence, it has been necessary to replace the fuel pipe each time a predetermined number of attachments and detachments have been carried out.
As described above, the conventional injector mounting structures have required many operating steps and working hours during periodical inspection work, and have entailed high maintenance costs. Also, the number of attachments and detachments of the fuel pipe is limited, and in order not to decrease the reliability of the connection of the fuel pipe, the fuel pipe needs to be replaced in good time. This has resulted in increased components costs.
Furthermore, the diesel engine for an automobile is a multi-cylinder engine such as a four- or six-cylinder engine. Thus, if a plurality of injectors in conformity with the number of the cylinders are detached, the relative positional relationship of the plurality of injectors with the cylinder head, and the relation between the common rail or the plurality of injectors and the fuel pipes may differ from those at the initial stage of assembly. Hence, much time and labor have been needed for readjustment at the time of reassembly.